The present invention relates to an antenna switch and a communication device and, more particularly, to a technique of adjusting power of a high frequency signal by means of an attenuating antenna switch configured to attenuate a signal in a controlled manner.
A communication device such as a cellular phone performs stationary communication with a base station as a relay device at the time of radio communication between communication devices. A communicatable range of one base station is called a cell. In one cell, a communication device adjusts transmission power of a high frequency signal and reception sensitivity in accordance with distance to the base station.
Generally, the transmission power has to be adjusted in the range of about −50 dBm to 30 dBm in accordance with the distance to the base station. The adjustment of the transmission power is performed by varying the gain of an RFIC (Radio Frequency Integrated Circuit) or an HPA (High Power Amplifier) mounted on a communication device.
On the other hand, at the time of adjusting the reception sensitivity, the gain of an LNA (Low Noise Amplifier) in an RFIC is varied so that reception power of a high frequency signal from a base station becomes a level at which the signal can be demodulated.
Patent literature 1 discloses a communication device in which a plurality of amplifiers having different gains are provided in parallel and an amplifier used for amplifying a high frequency signal is alternatively selected in accordance with transmission power or reception power to be satisfied. Patent literature 2 discloses an antenna switch for switching between transmission and reception of a high frequency signal in a time division manner.